ZFS Install Guide

Disclaimers

This guide will only show you how to install Funtoo/ZFS on a 64 bit system!

This guide is also using new technologies such as bliss-boot/initramfs/kernel. If you would like to use boot-update and or genkernel, please check out the ZFS Install Guide's Addendum.

This guide is a work in progress.

Introduction

In this guide we will show you how to install Funtoo on Native ZFS. The tutorial is meant to be an "overlay" over the Regular Funtoo Installation. Follow the normal guide during parts that are omitted.

Introduction to ZFS

Since ZFS is a new technology for Linux, it can be helpful to understand some of its benefits, particularly in comparison to BTRFS, another popular next-generation Linux filesystem:

On Linux, the ZFS code can be updated independently of the kernel to obtain the latest fixes. btrfs is exclusive to Linux and you need to build the latest kernel sources to get the latest fixes.

ZFS is supported on multiple platforms. The platforms with the best support are Solaris, FreeBSD and Linux. Other platforms with varying degrees of support are NetBSD, Mac OS X and Windows. btrfs is exclusive to Linux.

ZFS has the Adaptive Replacement Cache replacement algorithm while btrfs uses the Linux kernel's Last Recently Used replacement algorithm. The former often has an overwhelmingly superior hit rate, which means fewer disk accesses.

ZFS has the ZFS Intent Log and SLOG devices, which accelerates small synchronous write performance.

ZFS handles internal fragmentation gracefully, such that you can fill it until 100%. Internal fragmentation in btrfs can make btrfs think it is full at 10%. Btrfs has no automatic rebalancing code, so it requires a manual rebalance to correct it.

ZFS has raidz, which is like RAID 5/6 (or a hypothetical RAID 7 that supports 3 parity disks), except it does not suffer from the RAID write hole issue thanks to its use of CoW and a variable stripe size. btrfs gained integrated RAID 5/6 functionality in Linux 3.9. However, its implementation uses a stripe cache that can only partially mitigate the effect of the RAID write hole.

ZFS supports data deduplication, which is a memory hog and only works well for specialized workloads. btrfs has no equivalent.

ZFS datasets have a hierarchical namespace while btrfs subvolumes have a flat namespace.

ZFS has the ability to create virtual block devices called zvols in its namespace. btrfs has no equivalent and must rely on the loop device for this functionality, which is cumbersome.

The only area where btrfs is ahead of ZFS is in the area of small file
efficiency. btrfs supports a feature called block suballocation, which
enables it to store small files far more efficiently than ZFS. It is
possible to use another filesystem (e.g. reiserfs) on top of a ZFS zvol
to obtain similar benefits (with arguably better data integrity) when
dealing with many small files (e.g. the portage tree).

For a quick tour of ZFS and have a big picture of its common operations you can consult the page ZFS Fun.

Video Tutorial

As a companion to the installation instructions below, a YouTube video tutorial is now available:

Downloading the ISO (With ZFS)

In order for us to install Funtoo on ZFS, you will need an environment that already provides the ZFS tools. Therefore we will download a customized version of System Rescue CD with ZFS included.

Make sure the USB you want to use is unmounted before running the script, or it will fail. The script will partition, and mount your usb to /mnt/backup automatically.

Booting the ISO

Warning

Select the "Alternate 64 bit kernel (altker64)" option in the System Rescue CD Boot Menu. The ZFS modules have been built specifically for this kernel rather than the standard kernel. If you select a different kernel, you will get a fail to load module stack error message.

Creating partitions

There are two ways to partition your disk: You can use your entire drive and let ZFS automatically partition it, or you can do it manually.

We will be showing you how to partition it manually because if you do so, you get to create your own layout, you get to have your own separate /boot partition (Which is nice since not every bootloader supports booting from ZFS pools), and you get to boot into RAID10, RAID5 (RAIDZ) pools and any other layouts without any hassles due to you having a separate /boot partition.

gdisk (GPT Style)

A Fresh Start:

First lets make sure that the disk is completely wiped from any previous disk labels and partitions.
We will also assume that /dev/sda is the target drive.

# sgdisk -Z /dev/sda

Warning

This is a destructive operation and the program will not ask you for confirmation! Make sure you really don't want anything on this disk.

If you are using encrypted root, change /dev/sda4 to /dev/mapper/vault_1.

If you have a previous pool that you would like to import, you can do:
# zpool import -f -o cachefile= -R /mnt/funtoo <pool_name>

Create the zfs datasets

We will now create some datasets. For this installation, we will create a small but future proof amount of datasets. We will have a dataset for the OS (/). We will also show you how to create some optional datasets: /home, /var, /usr/src, and /usr/portage.

In Chroot

Add filesystems to /etc/fstab

Before we continue to compile and or install our kernel in the next step, we will edit the /etc/fstab file because if we decide to install our kernel through portage, portage will need to know where our /boot is, so that it can place the files in there.

Kernel Configuration

You can follow the kernel instructions in the normal guide, or you can install a pre-configured/compiled kernel called bliss-kernel. This kernel already has the correct configurations for ZFS and a variety of other scenarios. It's a vanilla kernel from kernel.org without any external patches.

To install sys-kernel/bliss-kernel (package not on wiki - please add) type the following:

# emerge bliss-kernel

Now make sure that your /usr/src/linux symlink is pointing to this kernel by typing the following:

You should see a star next to the version you installed. In this case it was 3.12.13-KS.02. If it's not set, you can type eselect kernel set #.

Installing the ZFS userspace tools and kernel modules

Emerge sys-fs/zfs (package not on wiki - please add). This package will bring in sys-kernel/spl (package not on wiki - please add), and sys-fs/zfs-kmod (package not on wiki - please add) as its dependencies:

# emerge zfs

Check to make sure that the zfs tools are working. The zpool.cache file that you copied before should be displayed.

# zpool status
# zfs list

If everything worked, continue.

Final configuration

Add the zfs tools to openrc

# rc-update add zfs boot

Clean up and reboot

We are almost done, we are just going to clean up, set our root password, and unmount whatever we mounted and get out.

Delete the stage3 tarball that you downloaded earlier so it doesn't take up space.
# cd /
# rm stage3-latest.tar.xz
Set your root password
# passwd
>> Enter your password, you won't see what you are writing (for security reasons), but it is there!
Get out of the chroot environment
# exit
Unmount all the kernel filesystem stuff and boot (if you have a separate /boot)
# umount -l proc dev sys boot
Turn off the swap
# swapoff /dev/sda3
Reboot
# reboot

Warning

Do not export the zpool. Just reboot. ZFS's zpool.cache file is shared between reboots and exporting the pool will cause problems. Exporting the pool is only meant when you want to move the zpool from one machine to another.

Important

Don't forget to set your root password as stated above before exiting chroot and rebooting. If you don't set the root password, you won't be able to log into your new system.

and that should be enough to get your system to boot on ZFS.

After reboot

Forgot to reset password?

System Rescue CD

If you aren't using bliss-initramfs, then you can reboot back into your sysresccd and reset through there by mounting your drive, chrooting, and then typing passwd.

Using bliss-initramfs

If you forgot to reset your password and are using bliss-initramfs, you can add the su option to your bootloader parameters and the initramfs will throw you into the rootfs of your drive. In there you can run 'passwd' and then type 'exit'. Once you type 'exit', the initramfs will continue to boot your system as normal.

Create initial ZFS Snapshot

Continue to set up anything you need in terms of /etc configurations. Once you have everything the way you like it, take a snapshot of your system. You will be using this snapshot to revert back to this state if anything ever happens to your system down the road. The snapshots are cheap, and almost instant.

To take the snapshot of your system, type the following:

# zfs snapshot -r tank@install

To see if your snapshot was taken, type:

# zfs list -t snapshot

If your machine ever fails and you need to get back to this state, just type (This will only revert your / dataset while keeping the rest of your data intact):

# zfs rollback tank/funtoo/root@install

Important

For a detailed overview, presentation of ZFS' capabilities, as well as usage examples, please refer to the ZFS Fun page.

Troubleshooting

Starting from scratch

If your installation has gotten screwed up for whatever reason and you need a fresh restart, you can do the following from sysresccd to start fresh:

Destroy the pool and any snapshots and datasets it has
# zpool destroy -R -f tank
This deletes the files from /dev/sda1 so that even after we zap, recreating the drive in the exact sector
position and size will not give us access to the old files in this partition.
# mkfs.ext2 /dev/sda1
# sgdisk -Z /dev/sda